The manufacture of electrical motors involves a balance of requirements for producing adequate output power without unnecessary expense. Electrical motors are comprised of a rotor that can be axially received within an opening in a stator. The stator typically has teeth that extend into the opening to form a diameter in which the rotor is received. Electrical conductors are mounted about the teeth to enable an electrical current in the conductors to generate a rotating magnetic field. The rotor is configured for rotation in response to the magnetic field generated by the stator. This rotor is fixedly mounted about a shaft that rotates with the rotor. This shaft is held by journal bearings at each end and endplates are mounted about each end of the housing in which the stator and rotor are positioned. The journal bearings hold the rotor in position and mounting members, typically bolts or other threaded members, pass through openings in one of the endplates and mounting holes within an outer portion of the stator to be received in a threaded opening in the other endplate to hold the stator in position. When the endplates are mounted about the rotor shaft and the bolts are received in the stator mounting holes and threaded openings in the endplate, the distance between a hub in one endplate through which the rotor shaft extends and a hub in the other endplate that also includes a journal bearing to hold the rotor shaft defines a hub-to-hub distance for the motor.
Some electrical motors are used in common applications with some variation in the output rating of the motor. For example, clothes dryers use an electrical motor to rotate a drum in which wet clothes are placed for heated air drying. Because the clothes hold water when they are first inserted in the drum, their weight can be significant. Consequently, clothes dryers have output ratings that typically range from ¼ horsepower (HP) to ½ HP. The output power of an electrical motor is related to the length of the rotor and stator in the axial direction of the rotor shaft and the thickness of the stator and the rotor in diameter of those components in a direction that is orthogonal to the axial direction. Holding the thickness of the stator and rotor constant, the length of the rotor and stator should vary as the output rating of the motor changes. This length variation, however, causes the hub-to-hub distance of the motor to change as well. Since the hub-to-hub distance is established by an industry standard, this hub-to-hub distance cannot extend beyond the tolerance range of the standard. Consequently, different output rated motors have stators and rotors of different lengths. Maintaining an inventory of different lengths of stators and rotors can be expensive and complicates the electrical motor manufacturing process. Simplifying the manufacture of electrical motors for different output ratings is desirable.